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Biomedical subjects

Stephen W Smith

Publications and source records attributed to Stephen W Smith.

At least 19 recordsLinked to original sources
PubMed2007

Sumatriptan for the treatment of undifferentiated primary headaches in the ED.

OBJECTIVE: In this study, we determine the effectiveness and adverse effects of sumatriptan when used in the emergency department (ED) as a first-line treatment for benign undifferentiated headaches, and determine if the International Headache Society (IHS) classification of migraine, probable migraine, or tension-type headache has any effect on the effectiveness of the treatment. We hypothesize that there is no difference in the effectiveness of pain relief or frequency and severity of adverse effects between patients with migraine, probable migraine, or tension-type headaches when treated with sumatriptan. METHODS: This was a prospective observational study of adult ED patients undergoing treatment for primary headaches (ie, patients in whom head trauma, vascular disorders, infection, or disorders of facial or cranial structures have been clinically excluded). Other exclusions were renal impairment, hepatic impairment, and risk factors for coronary artery disease. Consenting patients then were asked to complete a 100-mm visual analog scale (VAS) representing their perceived pain, after which they were interviewed by a research assistant who completed a headache diagnosis worksheet, which differentiates the headache by IHS criteria. The patient repeated the VAS score at 30 and 60 minutes. Data were analyzed using descriptive statistics and chi squared tests. RESULTS: One hundred forty-seven patients were enrolled: 84 (57.1%) patients with migraine headache, 45 (30.7%) with a probable migraine headache, and 18 (12.2%) with a tension headache. A 50% reduction in VAS scores 60 minutes postdose was seen in 87 (59%) of 147 patients; 50 (60%) of 84 of migraine patients, 25 (56%) of 45 of probable migraine patients, and 12 (67%) of 18 tension patients (P = .72). There were no serious adverse events reported. Forty-seven patients (32%) received rescue medications after the 60-minute VAS score: 29 (34.5%) patients in the migraine group, 15 (33.3%) patients in the probable migraine group, and 3 (15.8%) patients in the tension-type headache group (P = .26). CONCLUSIONS: Most of the patients presenting with primary headaches had migraine or probable migraine headaches. There was no difference in sumatriptan's effectiveness based on the classification of the headache using IHS criteria.

Adult↗
PubMed2006

ST segment elevation differs depending on the method of measurement.

OBJECTIVES: The literature seldom specifies the location or method of measurement of ST segment elevation (STE) for determining eligibility in reperfusion trials. The objective of this study was to assess if different methods of measurement of STE in precordial leads of patients with anterior acute myocardial infarction due to left anterior descending occlusion result in significantly different scores. METHODS: This was a retrospective review of diagnostic electrocardiograms (ECGs) of consecutive patients presenting to our emergency department with acute myocardial infarction who had emergent primary percutaneous coronary intervention, left anterior descending occlusion, and no bundle branch block. STE was measured at the J point and at 60 milliseconds after the J point, relative to the PR segment, in leads V1-V6. STE by the two methods was compared for each lead, as were ST scores (sum of STE in leads V1-V6) and the sum of the STE in V2-V4. Eligibility for reperfusion therapy using 1-mm and 2-mm STE criteria in two consecutive anterior leads, as well as ST scores and the sum of the STE in V2-V4, were evaluated. RESULTS: Thirty-seven ECGs were analyzed. Mean ST measurements in every lead were significantly lower when measured at the J point versus 60 milliseconds after the J point, as were ST scores (9.7 +/- 2.14 mm vs. 14.9 +/- 2.69 mm; p < 0.00001). Fewer ECGs met enrollment criteria when based on STE at the J point versus at 60 milliseconds after the J point. Fewer ECGs met an ST score of 6 mm when measured at the J point (70% vs. 88%). CONCLUSIONS: In anterior STE myocardial infarction, STE measurements produce different results depending on the method of measurement. Future clinical trials should specify the method of measurement.

Angioplasty, Balloon, Coronary↗
PubMed2006

Acute coronary syndromes.

Despite technologic advances in many diagnostic fields, the 12-lead ECG remains the basis for early identification and management of an acute coronary syndrome. This article reviews the use of the ECG in acute coronary syndromes.

Acute Disease↗
PubMed2006

Upwardly concave ST segment morphology is common in acute left anterior descending coronary occlusion.

ST elevation (STE) in anterior precordial leads, in association with upwardly convex morphology (M) or straightM, is associated with anterior acute myocardial infarction (aAMI). Upwardly concaveM is characteristic of pseudoinfarction patterns such as early repolarization. A retrospective review was done of diagnostic electrocardiograms (EKG) of consecutive patients presenting to our Emergency Department (ED) who underwent emergent primary percutaneous intervention (PCI) and had proven left anterior descending (LAD) occlusion. If all leads from V2-V6 were upwardly concave, the EKG was classified as concaveM. If one lead was convex, the EKG had convexM. If no leads were convex and at least one was straight, it had straightM. Non-concaveM was defined as either convexM or straightM. Borderline STE was defined if the EKG did not have 2 consecutive leads with >or= 2 mm of STE. "Subtle," as opposed to "diagnostic," morphology was defined as concaveM without terminal QRS distortion. Data were analyzed with descriptive statistics. There were 37 patients identified who met the inclusion criteria and whose records were available for review. ConcaveM was found in 16 of 37 (43%), 4 with terminal QRS distortion. Measurements resulted in a classification of borderline STE in 15 of 37 (41%) (9 of whom had subtle morphology) for Rater 1 and 12 of 37 (32%) (7 of whom had subtle morphology) for Rater 2, while 19% to 24% had both "subtle" morphology and borderline ST elevation. ConcaveM, as compared with convexM or terminal QRS distortion, was associated with a shorter duration of symptoms (p < 0.05). It is concluded that concave morphology cannot be used to exclude STEMI with LAD occlusion. Many patients with LAD occlusion have borderline ST elevation with subtle morphology. Concave morphology is associated with a shorter duration of symptoms.

Adult↗
PubMed2006

3-D ultrasound guidance of surgical robotics: a feasibility study.

Laparoscopic ultrasound has seen increased use as a surgical aide in general, gynecological, and urological procedures. The application of real-time, three-dimensional (RT3D) ultrasound to these laparoscopic procedures may increase information available to the surgeon and serve as an additional intraoperative guidance tool. The integration of RT3D with recent advances in robotic surgery also can increase automation and ease of use. In this study, a 1-cm diameter probe for RT3D has been used laparoscopically for in vivo imaging of a canine. The probe, which operates at 5 MHz, was used to image the spleen, liver, and gall bladder as well as to guide surgical instruments. Furthermore, the three-dimensional (3-D) measurement system of the volumetric scanner used with this probe was tested as a guidance mechanism for a robotic linear motion system in order to simulate the feasibility of RT3D/robotic surgery integration. Using images acquired with the 3-D laparoscopic ultrasound device, coordinates were acquired by the scanner and used to direct a robotically controlled needle toward desired in vitro targets as well as targets in a post-mortem canine. The rms error for these measurements was 1.34 mm using optical alignment and 0.76 mm using ultrasound alignment.

Animals↗
PubMed2006

Real-time, 3-D ultrasound with multiple transducer arrays.

Modifications were made to a commercial real-time, three-dimensional (3-D) ultrasound system for near simultaneous 3-D scanning with two matrix array transducers. As a first illustration, a transducer cable assembly was modified to incorporate two independent, 3-D intra-cardiac echo catheters, a 7 Fr (2.3 mm O.D.) side scanning catheter and a 14 Fr (4.7 mm O.D) forward viewing catheter with accessory port, each catheter using 85 channels operating at 5 MHz. For applications in treatment of atrial fibrillation, the goal is to place the sideviewing catheter within the coronary sinus to view the whole left atrium, including a pulmonary vein. Meanwhile, the forward-viewing catheter inserted within the left atrium is directed toward the ostium of a pulmonary vein for therapy using the integrated accessory port. Using preloaded, phasing data, the scanner switches between catheters automatically, at the push of a button, with a delay of about 1 second, so that the clinician can view the therapy catheter with the coronary sinus catheter and vice versa. Preliminary imaging studies in a tissue phantom and in vivo show that our system successfully guided the forward-viewing catheter toward a target while being imaged with the sideviewing catheter. The forward-viewing catheter then was activated to monitor the target while we mimicked therapy delivery. In the future, the system will switch between 3-D probes on a line-by-line basis and display both volumes simultaneously.

Algorithms↗
PubMed2006

Phase-aberration correction with a 3-D ultrasound scanner: feasibility study.

We tested the feasibility of using adaptive imaging, namely phase-aberration correction, with two-dimensional (2-D) arrays and real-time, 3-D ultrasound. Because of the high spatial frequency content of aberrators, 2-D arrays, which generally have smaller pitch and thus higher spatial sampling frequency, and 3-D imaging show potential to improve the performance of adaptive imaging. Phase-correction algorithms improve image quality by compensating for tissue-induced errors in beamforming. Using the illustrative example of transcranial ultrasound, we have evaluated our ability to perform adaptive imaging with a real-time, 3-D scanner. We have used a polymer casting of a human temporal bone, root-mean-square (RMS) phase variation of 45.0 ns, full-width-half-maximum (FWHM) correlation length of 3.35 mm, and an electronic aberrator, 100 ns RMS, 3.76 mm correlation, with tissue phantoms as illustrative examples of near-field, phase-screen aberrators. Using the multilag, least-squares, cross-correlation method, we have shown the ability of 3-D adaptive imaging to increase anechoic cyst identification, image brightness, contrast-to-speckle ratio (CSR), and, in 3-D color Doppler experiments, the ability to visualize flow. For a physical aberrator skull casting we saw CSR increase by 13% from 1.01 to 1.14, while the number of detectable cysts increased from 4.3 to 7.7.

Algorithms↗
PubMed2005

T/QRS ratio best distinguishes ventricular aneurysm from anterior myocardial infarction.

OBJECTIVES: Reperfusion therapy for acute myocardial infarction (AMI) is indicated in the presence of ST elevation (STE) and ischemic symptoms. Previous MI may present with persistent STE or "left ventricular aneurysm" (LVA) morphology that mimics AMI. Hypothesis A high ratio of T amplitude to QRS amplitude best distinguishes AMI from LVA. METHODS: This was a retrospective cohort analysis. Patients with anatomical LVA by echocardiography were identified and those who presented to the ED with ischemic symptoms and STE of at least 1 mm in 2 consecutive leads and ruled out for acute left anterior descending coronary artery (LAD) occlusion were selected. Electrocardiograms (ECGs) were compared with a control group of 37 consecutive anterior AMI (aAMI) with proven acute LAD occlusion. Bundle-branch block was excluded. Various ECG measurements and ratios were compared. RESULTS: Twenty patients with LVA met the inclusion criteria. The best discriminator was T amplitude sum to QRS amplitude sum ratio V1-V4, misclassifying only 4 (6.8%) of 59 cases at a cutoff of >0.22 for AMI. For aAMI and LVA, respectively, mean (+/-95% CI) ratio of the sum of T amplitudes in V 1 to V 4 to the sum of QRS amplitude in V1-V4 was 0.54+/-0.085 and 0.16+/-0.021 (P<.00012). Thirty-five of 37 aAMI had a ratio>0.22; the false negatives (ratio<0.22) had 11.5 and 6 hours of symptoms before the ECG. Twenty of 22 LVA had a ratio<or=0.22. Mean highest T/QRS ratio in V1-V4 was 1.1+/-0.29 for an AMI and 0.26+/-0.056 for LVA (P<10(-7)). CONCLUSION: T amplitude/QRS amplitude ratio best distinguishes aAMI from LVA in ECGs that meet STE criteria for reperfusion therapy. A high ratio is associated with an AMI.

Adult↗
PubMed2005

Agitation is common in gamma-hydroxybutyrate toxicity.

Gamma-Hydroxybutyrate (GHB)-related compounds are most commonly described as depressants, with emphasis on somnolence, obtundation, stupor, and coma (SOSC). We sought to demonstrate the full spectrum of clinical presentations of GHB intoxication, including agitation and other nonsedative effects. Our observational study identified 66 patients with GHB toxicity, 40 of whom manifested agitation; 25 had agitation before or after SOSC, 10 had agitation alternating abruptly with SOSC, and 5 had agitation only. Fourteen presentations also included "bizarre" or self-injurious behaviors. Of 40 presentations with agitation, 19 had stimulant co-intoxicants confirmed by screen (14) or history (5). The remaining 21 patients with agitation were negative for stimulants by screen (12) or history (9). Gas chromatography/mass spectrometry detected GHB in 25 cases; 12 manifested agitation, 4 of which also screened negative for stimulants. Clinicians should broaden their definitions of GHB toxicity to include nonsedative effects such as agitation, combativeness, and bizarre or self-injurious behavior.

Adjuvants, Anesthesia↗
PubMed2005

Finite-element analysis of temperature rise and lesion formation from catheter ultrasound ablation transducers.

A model using finite-element analysis (FEA) has been developed to calculate the temperature rise in tissue from intracardiac ultrasound ablation catheters and to predict if this temperature rise is adequate for producing a lesion in the tissue. In the model, acoustic fields are simulated with Field II, and heat transfer is modeled with an FEA program. To validate the model, we compare its results to experimental results from an integrated, real-time three-dimensional (3-D) ultrasound imaging and ultrasound ablation catheter. The ultrasound ablation transducer is a ring transmitting at 10 MHz capable of producing an acoustic intensity of 16 W/cm2. It was used to ablate four lesions in tissue, and temperature rise as a function of time was monitored by embedded thermocouples. The average absolute difference between final temperatures predicted by FEA and those measured is 1.95 +/- 0.72 degrees C. Additionally, model and experimental lesion size are in good agreement. The model then is used to design a new ultrasound catheter with a 7.5 MHz linear phased array for ablation. Eight designs are modeled, and acoustic intensity, temperature rise, and ablation ability are compared.

Animals↗
PubMed2005

Catheter ultrasound phased-array transducers for thermal ablation: a feasibility study.

The feasibility of catheter single-element ultrasound transducers for cardiac ablation has been shown previously. We describe the design and testing of catheter-sized linear phased arrays transducers for ultrasound ablation. One array has 86 PZT-4 elements operating at 8 MHz and 5 MHz. The overall array size is 14.9 mm by 3.1 mm (10 Fr). The other array has 50 PZT-5 elements operating at 4 MHz and is 17 mm by 3.1 mm (10 Fr). In order to produce the intensity needed to create lesions in heart tissue, we modified a real-time, 3D scanner to produce 100 Vpp 256-cycle transmit pulses at a pulse repetition frequency of 14.1 kHz. This made it possible for the PZT-4 and PZT-5 transducers to produce ISPTA of 3.26 W/cm2 and 142 W/cm2, respectively. When driving the transducers at high duty factor, the transmit circuitry in the scanner was damaged. A mechanically-focused transducer with the same dimensions as the PZT-4 transducer was built. When transmitting continuously at 9 MHz, it produced an ISPTA of 29.3 W/cm2. This created a lesion 5 mm across and 5 mm deep in beef tissue while raising the focal temperature 23 degrees C. Ablation is within the capabilities of a catheter phased array transducer integrated into a diagnostic ultrasound scanner.

Catheter Ablation↗
PubMed2005

Real-time 3D laparoscopic ultrasonography.

We have previously described 2D array ultrasound transducers operating up to 10 MHz for applications including real time 3D transthoracic imaging, real time volumetric intracardiac echocardiography (ICE), real time 3D intravascular ultrasound (IVUS) imaging, and real time 3D transesophageal echocardiography (TEE). We have recently built a pair of 2D array transducers for real time 3D laparoscopic ultrasonography (3D LUS). These transducers are intended to be placed down a trocar during minimally invasive surgery. The first is a forward viewing 5 MHz, 11 x 19 array with 198 operating elements. It was built on an 8 layer multilayer flex circuit. The interelement spacing is 0.20 mm yielding an aperture that is 2.2 mm x 3.8 mm. The O.D. of the completed transducer is 10.2 mm and includes a 2 mm tool port. The average measured center frequency is 4.5 MHz, and the -6 dB bandwidth ranges from 15% to 30%. The 50 omega insertion loss, including Gore MicroFlat cabling, is -81.2 dB. The second transducer is a 7 MHz, 36 x 36 array with 504 operating elements. It was built upon a 10 layer multilayer flex circuit. This transducer is in the forward viewing configuration and the interelement spacing is 0.18 mm. The total aperture size is 6.48 mm x 6.48 mm. The O.D. of the completed transducer is 11.4 mm. The average measured center frequency is 7.2 MHz, and the -6 dB bandwidth ranges from 18% to 33%. The 50 omega insertion loss is -79.5 dB, including Gore MicroFlat cable. Real-time in vivo 3D images of canine hearts have been made including an apical 4-chamber view from a substernal access with the first transducer to monitor cardiac function. In addition, we produced real time 3D rendered images of the right pulmonary veins from a right parastemal access with the second transducer, which would be valuable in the guidance of cardiac ablation catheters for treatment of atrial fibrillation.

Animals↗
PubMed2005

The killing of severely disabled newborns: the spectre behind the legalisation of physician-assisted suicide and euthanasia.

Arguments made by those in favour of the legalisation of physician-assisted suicide (PAS) and euthanasia often rely upon the idea of the quality of life. This idea states that an individual's life is not valuable as an intrinsic good, but is only good based upon the things which it allows us to do. It thus allows the argument that it is morally permissible to kill individuals whose lives have fallen below an acceptable 'quality of life.' However, this concept may require that one accept the killing of individuals who have not expressly request to be killed such as severely disabled newborns. This paper will examine the issue of whether those who utilise a quality of life approach to justify the legalisation of PAS and euthanasia must logically accept the policy of killing severely disabled newborn children. First, there will be an examination of the concept of quality of life and its importance in the arguments for the legalisation of PAS or euthanasia. This paper will then consider how notions of personhood interact with the concept of quality of life in order to create the problem faced by those who favour the legalisation of PAS or euthanasia. Finally, this paper will consider how the notion of autonomy may be used as a way to avoid this difficulty created by the quality of life approach.

Congenital Abnormalities↗
PubMed2004

Outcome of low-risk patients discharged home after a normal cardiac troponin I.

Patients with symptoms suggestive of, but at low risk for, acute coronary syndrome (ACS), who have a negative electrocardiogram (EKG) and a single normal troponin I at 6-9 h after symptom onset are frequently discharged from our Emergency Department (ED). We sought to determine their rate of adverse cardiac events at 30 days (ACE-30), defined as cardiac death or myocardial infarction (MI), by chart review, telephone interview, or county death records. Of 663 patients, data were available for 588 (89%). Mean age was 48 years; 59% were male. There were 390 patients (66%) who complained of chest pain. Previous coronary artery disease (CAD) was reported in 145 patients (25%). Two patients (0.34%) had ACE-30, both with non-ST elevation MI. There were no cases of cardiac death. None of the patients died in Hennepin County within 30 days. At our institution, low-risk patients with symptoms suggestive of ACS who are discharged home after a normal cTnI drawn 6-9 h after symptom onset have a very low incidence of cardiac events at 30 days.

Angina, Unstable↗